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  • Articles: DFG German National Licenses  (11)
  • 1995-1999  (6)
  • 1990-1994  (5)
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  • Articles: DFG German National Licenses  (11)
Material
Years
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Spot welder for making small electrical contacts (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2747-2756 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A capacitive-discharge spot welder is described which is primarily intended for making electrical connections between small (〈25–150 μm diameter) wires and samples of metallic materials, although it can be used in many applications where miniature welds must be made. It has been particularly useful in allowing low resistance (several mΩ) contacts to be created on samples of rare earth and actinide intermetallic compounds which are highly resistant to soldering. The device has a minimum time constant of about 25 μs and can deliver a maximum of between 700 μJ and 400 mJ of energy to the weld region, depending on the resistance of the latter. A suitable electrode holder is also described, and considerations for choosing the electrode materials, selecting the contact wires, preparing the sample, and creating a weld are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149010
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Circulation pump for high purity gases at high pressures and a novel linear motor positioning system (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 564-578 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A clearance-sealed piston pump has been developed which can be used to move high pressure gases in a closed loop for the purpose of purification, mixing, or phase equilibration. It has been designed primarily with the former role in mind, so that inert gases may be used in the preparation of high purity intermetallic compounds to suppress the evaporation of volatile constituents without introducing contamination. To this end, the device is made in such a way as to minimize outgassing, leakage, the formation of dead volumes, and the creation of debris. The pump is intended for use at pressures of up to 200 bar. Its structural materials are highly resistant to corrosion, and this should enable the device to be used with a wide variety of reactive gases. Flow rates of between 4.3 and 0.043 l min−1 can be sustained without difficulty using realistic loads, although larger and smaller ones are possible. The pump is capable of producing a head of 0.23 bar. A novel system has been developed for sensing and controlling the position of the piston. This makes it possible to monitor and vary the instantaneous flow rate while minimizing wear and vibration. The arrangement does not require the presence of a transducer or any kind of feedthrough in the clean, high pressure environment. It may find applications in other areas where positioning is needed under hostile or demanding conditions, such as inside ultrahigh vacuum apparatus. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146637
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Method for making electrical contacts to hard and reactive intermetallic compounds (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 247-250 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method is described for making electrical contacts to metallic materials which, because of their hardness and reactivity, can be very difficult to attach leads to using other techniques. These metals, including some of the heavy fermion materials, form inert and tightly bonded oxide layers which hinder the use of ordinary soldering methods. It has been found that a simple modification to an ordinary soldering iron, involving the replacement of the standard copper tip with one made of tungsten carbide, enables these oxide layers to be penetrated and electrical contact to be made without the use of flux. The size of the resulting contacts can be very small and their electrical resistance very low. Other, less viable, techniques for making contacts are also discussed, and a means of holding samples in place during soldering is described. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145265
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Small dc motor for producing motion in a cryogenic environment, and a method for monitoring its orientation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 814-820 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In the field of condensed matter physics, it is frequently necessary to produce motion at low temperatures. While this can often be done using a mechanical linkage which connects the cryogenic and ambient environments, space constraints sometimes render such a solution impractical. The following paper describes a miniature dc electric motor which can be used to produce motion under these conditions, and also presents a novel scheme for monitoring its position. The motor is a skew-wound ironless device with a coaxial gearhead, and is capable of operating at a temperature of 4 K, in a vacuum, and in a magnetic field of several hundred gauss. The position monitoring arrangement requires no modifications to the motor or the addition of extra hardware, such as rotary encoders or potentiometers. Based on the angular dependence of the rotor inductance, it has been found to work with a number of different motors of the skew-wound ironless type, both at room temperature and at 4°. Provisions have been made to allow the motor and position monitor to be operated by computer control. The author anticipates that they will find applications in other areas where motion is needed and space is at a premium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144165
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Nonmagnetic piston–cylinder pressure cell for use at 35 kbar and above (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3402-3412 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A piston–cylinder cell has been constructed which makes it possible to achieve pressures of over 35 kbar at room temperature, and more than 29 kbar in a cryogenic environment. The use of a nonmagnetic cobalt–nickel alloy with an unusually high yield strength (1.97 GPa at 293 K) allows the cell to be used in the presence of large magnetic fields. It seems likely that the cobalt–nickel material can be used as a direct replacement for the celebrated (but largely unavailable) Russian nickel alloy in many applications where nonmagnetic pressure cells are needed. Such applications may also include other kinds of high pressure apparatus, such as diamond anvil and sapphire anvil cells. The pressure cell described in the present article employs the "Teflon cap" technique, and detailed information concerning the application of this method is given which can be used with a wide variety of cells of the piston–cylinder type. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149927
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Causes of death in Canadians with haemophilia 1980–1995 (1998)
    Oxford UK : Blackwell Science Ltd
    Haemophilia 4 (1998), S. 0 
    Details
    ISSN: 1365-2516
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The life expectancy of individuals with haemophilia was close to that of the general population in the early 1980s. Since then, life expectancy has decreased, due to transfusion-transmitted virus infections. Deaths in individuals with haemophilia were investigated by analysing 2450 records from the Canadian Hemophilia Registry, for the years 1980–1995. Deaths were tabulated by age, year and cause, and compared with that of the Canadian male population by calculating standardized mortality ratios (SMRs). The median life expectancy at 1 year of age was calculated for various subpopulations and the impact of various population characteristics was assessed by survival regression modelling. There were 359 deaths and the annual number of deaths increased significantly after 1986. Risk factors were seropositivity to human immunodeficiency virus (relative risk 16.7, 95%CI 11.1–25.1), severe haemophilia (1.9, 1.3–2.7) and moderate haemophilia (1.8, 1.2–2.6). In HIV antibody negative individuals, the overall death rate was not increased (SMR 0.9, 95%CI 0.7–1.1) and only haemorrhage was significantly increased. In HIV antibody positive individuals, causes of death which were significantly increased were acquired immunodeficiency syndrome, liver failure, haemorrhage, lymphoma, liver cancer, nonspecific infections, and trauma or violence. Deaths due to the acquired immunodeficiency syndrome accounted for only 66% of the excess deaths in individuals who were HIV antibody positive. Life expectancy has markedly decreased since the onset of the HIV epidemic. The impact of HIV is underestimated by considering only deaths due to the acquired immunodeficiency syndrome; other HIV-linked causes need also to be considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2516.1998.00179.x
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetically mediated superconductivity in heavy fermion compounds (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 394 (1998), S. 39-43 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In a conventional superconductor, the binding of electrons into the paired states that collectively carry the supercurrent is mediated by phonons — vibrations of the crystal lattice. Here we argue that, in the case of the heavy fermion superconductors CePd2Si2 and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/27838
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  • 8
    Electronic Resource
    Electronic Resource
    Climatic and limnological changes associated with the Younger Dryas in Atlantic Canada (1993)
    Springer
    Climate dynamics 8 (1993), S. 177-187 
    Details
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Pollen, diatom and chironomid fossils from the sediments of a core from Brier Island Bog Lake, Nova Scotia were studied in an attempt to relate changes in microfossil composition to a climatic cooling in Atlantic Canada correlative with the European Younger Dryas ca. 10 to 11 ka. Our paleolimnological data were then compared to similar types of data from Splan Pond, New Brunswick to determine if there were any significant differences between a coastal and a more inland site. Nonarboreal pollen was dominant throughout the Brier Island core and the interval 10.0–11.0 ka did not show the typical decline in Picea and increases in tundra-like vegetation characteristic of many sites in Atlantic Canada. However, the limnological indicators did undergo marked changes in taxon composition. The chironomid assemblage was initially dominated by shallow-water, warm-adapted chironomid taxa followed by abundant Sergentia (a cold stenotherm) during 10–11 ka. Sergentia disappeared in the “post Younger Dryas” interval and the warm-adapted genera resumed dominance. Chironomid-inferred paleotemperature reconstructions revealed that at both Brier Island Bog Lake and Splan Pond, summer surface-water temperatures dropped abruptly to between 13 and 17°C during the 10–11 ka interval, suggesting that a cooler climate was present in Atlantic Canada correlative with the European Younger Dryas. Diatom assemblage changes during the same period corroborate the occurrence of limnological fluctuations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00207964
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  • 9
    Electronic Resource
    Electronic Resource
    The larva and habitat ofParakiefferiella nigra Brundin (Diptera: Chironomidae) (1992)
    Springer
    Aquatic ecology 26 (1992), S. 527-531 
    Details
    ISSN: 1573-5125
    Keywords: palaeolimnology ; Chironomidae ; taxonomy ; larval subfossils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Collections of adults ofParakiefferiella nigra Brundin indicate that this chironomid occurs widely in arctic and subarctic zones. In addition, it has occasionally been collected in cool temperate and boreal forest lakes of both North America and Europe. Although widely distributed, the larva and its habitat have not previously been described. Identity of the larva ofP. nigra has been established by studying associated reared specimens. The distinctive larva, with reduced second lateral mental teeth, is stenotopic, and on the basis of modern collections appears to be most abundant in cold, oligotrophic lakes. More data is required to establish the range of thermal environments inhabited by the larva. Larval head capsule remains ofP. nigra are common in late-glacial sediments of southwestern British Columbia lakes and provide important evidence for oligotrophic conditions during late-glacial time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255286
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  • 10
    Electronic Resource
    Electronic Resource
    The observation of resistance oscillations in metals at high magnetic fields using a SQUID (1993)
    Springer
    Journal of low temperature physics 90 (1993), S. 205-241 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Quantum oscillatory effects provide particularly unambiguous information about the properties of quasiparticles in metals, and have consequently been used for the purpose of understanding the low temperature behaviour of a wide variety of metallic elements and compounds, including the recently discovered heavy fermion materials. Unfortunately, the signals which are produced by these oscillations are often so weak as to be undetectable, because of the high effective masses of the quasiparticles, or the presence of imperfections in the samples, or otherwise. In order to improve our ability to measure these effects, the author has developed a system for the detection of resistance oscillations which uses a SQUID as the amplifying element and which fits inside a toploading dilution refrigerator probe. It has proven possible to use this instrument to investigate very elusive phenomena in samples which have been cooled to 0.02 K in magnetic fields of 13.7 tesla. For example, although no resistance oscillations have previously been seen in aluminum, except under conditions of magnetic breakdown, the new system has made it possible to detect resistance oscillations in this material under relatively arbitrary conditions. In the case of the heavy fermion compound CeRu2Si2, oscillations of 10−9 Ω have been detected against a background resistance of about 10−5 Ω, using excitation currents of around 10−2 A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682000
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